fix documentation on choco_install_timeout

… present)

This makes the module work with puppet agent again. Server version is only
checked if the corresponding fact is defined.

fix issue #105 (Error when using puppet apply (the serverversion fact is not present))

Fixes travis tests (for puppet 3 and puppet 4) and adds
validation to init.pp as expected by existing tests.

Fix tests chocolatey download url

Introducing new parameter chocolatey_version for class
chocolatey. Fallback to chocolateyversion fact. Does not
change existing behaviour but extends the module
interface with the new parameter.

(GH-110) $::chocolateyversion fact always necessary

Changed use_7zip from 'true' to 'false'

Fixing: chocolatey-archive#117

Changed use_7zip from 'true' to 'false'

PowerShell v2/3 caches the output stream. Then it throws errors due to
the FileStream not being what is expected. Fixes "The OS handle's
position is not what FileStream expected. Do not use a handle
simultaneously in one FileStream and in Win32 code or another
FileStream."

The fix comes from
http://www.leeholmes.com/blog/2008/07/30/workaround-the-os-handles-position-is-not-what-filestream-expected/
plus information in the comments that actually makes it work.

The Chocolatey install PowerShell script has been signed
at dot org and all of the scripts in Chocolatey 0.9.10 are
being signed, so it is appropriate to sign this script as
well for the benefit of folks who would need that.